The Newly Collected Wild Cacao Germplasm from Peruvian Amazon and Its Implication for Disease Resistance

Diverse cacao (Theobroma cacao L.) germplasm is fundamental to breeding new varieties for resistance to diseases and pests, for environmental adaptation and for superior cacao bean quality.  However, the genetic potential in cacao germplasm, especially the wide range of wild populations that spontaneously grow in the Amazon rainforest, is poorly known.  Since 2008, four different collecting expeditions have been carried out in the Department of Amazonas, Loreto, San Martin, Ucayali and Madre de Dios.  Four hundred and fifty wild cacao trees from 17 river basins have been collected as budwood cuttings and propagated in the field genebank of  Instituto de Cultivos Tropicales (ICT), Tarapoto, Peru.  Molecular characterization using SNP and SSR markers revealed that this new  cacao collection has highest gene diversity and allele richness among all existing wild cacao collections. This collection is now being evaluated   at Tarapoto Peru for resistance to frosty pod rot - Moniliophthora roreri, witches’ broom - Moniliophthora  perniciosa, and black pod rot -Phytophthora palmivora. QTL mapping, based on SNP chip genotyping and genome-wide association, will be applied to discover new sources of resistance to major diseases of  cacao.